Dsl_Dog_Treat
I lost my face to the jaws of a poodle
A more compelling concern to me though is that this doesn't do anything for the primary issue. Generally, the cause of the leaks is old stiff O-rings. This will continue to be a problem regardless of if it's a plastic fitting or metal. If anything I think the rigidity of the metal rail and expansion issues would put more stress on the o-rings and make them more likely to leak. I would also question the surface finish of the o-ring seat in the rail. If this surface is rough, which is may be depending on how it is machined, then I would expect this to also potentially cause shortened o-ring life.
IMHO, the only issue with the plastic return line fittings is damage from external issue - ie you break them working on something else. I could be wrong, but I don't think there's much issues with them spontaneously breaking. Likewise the rubber return lines have a reasonable life expectancy. Yes, it's not infinite, but they last pretty well. Easy and cheap enough to fix as well. Beyond that, you still have the rubber hose to fuel filter, injection pump, and back to the tank to potentially leak.
IMHO, not worth the cost.
My same concerns as well. The Delphi and Diapco kits have served well over the years. Working on them, I only had issues for a short time with a bad batch of caps that had bit of flash that got past the molds creating some trimming and cleaning issues to avoid cutting orings.
Other than that, I see them being less forgiving on aging orings over a straight rail. The rails do look cool tho, but a lot of us run these platforms for their durability and low cost maintenance to operate. Nothing wrong with pushing the envelope for development tho.